An X-ray CT apparatus reconstructs a tomographic image of an object by using projection data obtained at a plurality of angles by causing an X-ray tube device, which irradiates an object with X-rays, and an X-ray detector, which detects an X-ray dosage transmitted through an object as projection data, to rotate around the object, and the apparatus displays the reconstructed tomographic image. The image displayed by the X-ray CT apparatus gives a picture of a shape of an internal organ in the object and is used in diagnostic imaging.
A rotary anode type X-ray tube device, which causes a disk-shaped anode to rotate, is used as the X-ray tube device used in the X-ray CT apparatus. Since the rotary bearing that rotatably supports the anode is used in an evacuated and high-temperature environment, a solid lubrication film made of soft metal as a main component, such as lead or silver, is widely used as a lubricant of the rotary bearing. However, since the solid lubrication film is only mechanically in close contact with front surfaces of bearing balls, an inner ring, and an outer ring that configure the rotary bearing, the film peels off depending on a use state in some cases. When the peeled-off solid lubrication films scatter in an X-ray tube, various problems such as discharge arise.
PTL 1 discloses a structure in which a cap is provided in the vicinity of a rotary bearing in order to reduce scattering of peeled-off solid lubrication films in an X-ray tube.